1. Field of the Invention
This invention relates to microemulsion defoamer compositions and their use in defoaming aqueous systems containing foam producing solids.
2. Description of the Prior Art
U.S. Pat. No. 2,715,614--Snook, issued Aug. 16, 1955 describes a defoamer composition for paper machines which is a white semi-fluid aqueous emulsion containing a paraffin hydrocarbon having at least 12 carbon atoms, a partial ester of a polyhydric alcohol and a fatty acid having 14 to 22 carbon atoms, an ester of a monohydric alcohol having less than 9 carbon atoms and a fatty acid having 14 to 22 carbon atoms, an ester of a polyethylene glycol having a molecular weight of from about 200 to about 4000 and a fatty acid having from 14 to 22 carbon atoms and water.
U.S. Pat. No. 2,843,551--Leonard et al, issued July 15, 1958 describes a defoamer composition for latex paint which is a cream colored paste containing a paraffin hydrocarbon, an ester of a polyethylene glycol having a molecular weight greater than 400 and a fatty acid having from 12 to 22 carbon atoms, an aliphatic carboxylic acid having from 6 to 22 carbon atoms and a hydrocarbon soluble organo-polysiloxane having from 1 to 3 alkyl radicals per silicon atom and water.
U.S. Pat. No. 4,032,473--Berg et al, issued June 28, 1977, describes a water based defoamer composition containing a water insoluble mineral hydrocarbon, solid fatty acid diamide, hydrophobic silica particles and a nonionic emulsifier which is a stearyl alcohol ethoxylate. The composition is homogenized to obtain a stable pumpable emulsion having the appearance and consistency of heavy cream.